Polyurethane Toughened Polystyrene With In-Situ Compatibilization and Controlled Hierarchical Microphase Structure by "One-Pot" Cascade Radical and Step-Growth Polymerizations

The microphase structure of multicomponent and multiphase polymers plays a critical role in determining their properties. A one-pot strategy integrating radical and step-growth polymerizations is developed to prepare polyurethane (PU)/polystyrene (PS) alloy (PUS) with a high-impact polystyrene (HIPS)-like salami morphology. Di-(6-hydroxylhexyl) maleate (HMH) is introduced as a dual-role monomer to form PS-g-PU as a compatibilizer in situ. When dibutyltin dilaurate (DBTDL) was initially mixed with poly(tetramethylene glycol), HMH, 4,4'-methylenebis(phenyl isocyanate), and styrene, delaying benzoyl peroxide (BPO) addition allowed the PU particles (0.1∼0.3 µm) to aggregate into larger PU microdomains. In contrast, when BPO was initially mixed with the monomers, delaying DBTDL addition promoted the formation of PS-grafted HMH, followed by their incorporation into PU chains and forming a salami-like morphology. The optimized PUS exhibited a notched impact and tensile strengths of 10.1 kJ/m² and 45.5 MPa, respectively (9.4 kJ/m² and 30.9 MPa for commercial HIPS). This work provides a one-pot route for coupling chain-growth and step-growth polymerizations to prepare PUS with controlled phase structures and in-situ compatibilization.